Dynamic phased array tapering without phase recalibration

ABSTRACT

Variable gain amplifiers and methods of designing the same include a first amplifying transistor configured to receive a first input signal and to provide a first amplified output signal based on the first input signal. A phase compensating resistor is connected to the first amplifying transistor and has a resistance calibrated as: 
     
       
         
           
             
               R 
               e 
             
             = 
             
               
                 τ 
                 b 
               
               
                 C 
                 
                   be 
                   , 
                   par 
                 
               
             
           
         
       
     
     where τ b  is the base transit time of the first amplifying transistor and C be,par  is the gain-independent part of the base-emitter capacitance of the first amplifying transistor.

BACKGROUND Technical Field

The present invention relates to phased array transceivers and, moreparticularly, to tapering in phased array systems to improvetransmission and reception pattern characteristics.

Description of the Related Art

A phased array system uses an array of antenna elements for a singletransmitter or receiver. By adjusting a phase shift between antennaelements, the gain of the entire array can be precisely directed duringoperation, making it possible to achieve high gains with pinpointaccuracy.

However, while the highest gain is focused on the main lobe of thearray's emission pattern, side lobes may also exist. Side lobesrepresented waste in the potential gain of the antenna array, as gainthat could be directed along the main lobe is instead oriented off tothe side. In addition, side lobes create interference in undesireddirections in transmitter mode and allow the reception of interferingsignals from undesired directions in receiver mode.

In a phased array, the direction of the main lobe is set by the phasesetting applied to each element. Tapering is used to control the sidelobes by controlling the gain of an amplifier at each antenna element.Ideally, varying the gain at each element should not change the phase,otherwise the direction of the main lobe changes and/or sidelobes may beaffected as well. Ideally, phase shifting in an element should not varythe gain. In practice, phase and gain adjustment are non-orthogonal,making calibration and tapering challenging. Variable gain amplifiers(VGAs) exhibit different phase for different gain settings and phaseshifters typically show gain/loss variations with phase settings aswell.

For these reasons, conventional systems determine a correct gain andphase iteratively, setting the gain and phase of antenna front-ends inturn until the desired overall gain and phase of the front-end isachieved. This decreases the responsiveness of the system and limits itsability to quickly adapt to changing needs. In addition, as the size andspatial resolution of the array increase, then the number of gain andphase settings needed increases in turn. For large systems, the memorydemands can become impractical, particularly if they are deployed atsmall scale on an integrated circuit.

SUMMARY

A variable gain amplifier includes a first amplifying transistorconfigured to receive a first input signal and to provide a firstamplified output signal based on the first input signal. A phasecompensating resistor is connected to the first amplifying transistorand has a resistance calibrated as:

$R_{e} = \frac{\tau_{b}}{C_{{be},{par}}}$

where τ_(b) is the base transit time of the first amplifying transistorand C_(be,par) is the gain-independent part of the base-emittercapacitance of the first amplifying transistor.

A variable gain amplifier include a first amplifier configured toreceive a first input signal and to provide a first amplified outputsignal based on the first input signal. A second amplifier is configuredto receive a second input signal and to provide a second amplifiedoutput signal based on the second input signal. A phase compensatingresistor is connected to the first amplifier and to the second amplifierand has a resistance that compensates for a phase dependence of thefirst amplifier, such that an output phase of the amplified outputsignal is dependent only on the phase of the input signal and isindependent of an amplification of the first amplifier.

A method of constructing a variable gain amplifier includes designingout a circuit for a first variable gain amplifier. The first variablegain amplifier includes a first amplifying transistor configured toreceive a first input signal and to provide a first amplified outputsignal based on the first input signal and a phase compensating resistorconnected to the first amplifying transistor and having a resistancethat compensates for a phase dependence of the first amplifyingtransistor. An output phase of the amplified output signal is dependentonly on a phase of the input signal and is independent of anamplification of the first amplifying transistor. Parameters of thefirst amplifying transistor are determined. A resistor degenerationvalue is determined based on the parameters of the first amplifyingtransistor as:

$R_{e} = \frac{\tau_{b}}{C_{{be},{par}}}$

where τ_(b) is the base transit time of the first amplifying transistorand C_(be,par) is the gain-independent part of the base-emittercapacitance of the first amplifying transistor. The first variable gainamplifier is constructed with the phase compensating resistor having aresistance equal to the resistor degeneration value.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a diagram of a phased-array transceiver in accordance with thepresent principles;

FIG. 2 is a block/flow diagram of a method for tapering control in aphased-array transceiver in accordance with the present principles;

FIG. 3 is a circuit diagram of a phase-invariant variable gain amplifierin accordance with the present principles;

FIG. 4 is a block/flow diagram of a method of designing a single-stage,phase invariant variable gain amplifier in accordance with the presentprinciples;

FIG. 5 is a circuit diagram of a phase-invariant variable gain amplifierin accordance with the present principles;

FIG. 6 is a diagram of a two-stage, phase-invariant variable gainamplifier in accordance with the present principles;

FIG. 7 is a diagram of phase and gain relationships in a two-stage,phase invariant variable gain amplifier in accordance with the presentprinciples;

FIG. 8 is a block/flow diagram of a method of designing a two-stage,phase invariant variable gain amplifier in accordance with the presentprinciples;

FIG. 9 is a circuit diagram of a phase-invariant variable gain amplifierand phase shifter in accordance with the present principles;

FIG. 10 is a circuit diagram of a phase-invariant variable gainamplifier and phase shifter in accordance with the present principles;

FIG. 11 is a block diagram of a phased array front-end control system inaccordance with the present principles;

FIG. 12 is a circuit diagram of various embodiments of a phase-invariantvariable gain amplifier in accordance with the present principles

FIG. 13 is a circuit diagram of a variable degenerating resistor inaccordance with the present principles; and

FIG. 14 is a block diagram of an amplifier design system in accordancewith the present principles.

DETAILED DESCRIPTION

Embodiments of the present invention provide phase-invariant gaincontrol for tapering. In the context of the present embodiments,“phase-invariant gain control” refers to a phase change caused by anamplifier, where that phase change is invariant across different gainsettings. By making the phase shift of a variable gain amplifierinvariant with respect to changes in gain, the number of differentsettings can be reduced and the responsiveness of the phased arraysystem can be dramatically increased. Whereas in conventional systems,particularly at high frequencies (e.g., in the millimeter wave band) thephase of the amplifier may depend strongly on the gain setting, thepresent embodiments provide such amplifiers with greatly diminished ornegligible phase dependency.

Referring now to FIG. 1, a phased array system is shown having aplurality of radio frequency (RF) front-ends 100, each with a respectiveantenna element 102. Each RF front-end 100 includes a pair ofreceive/transmit switches 106 that switch between a receive path leadingaway from the antenna element 102 and a transmit path leading to theantenna element 102. Each of the transmit and receive paths include alow-noise amplifier (LNA) 108 and a phase-invariant variable gainamplifier (VGA) 110. A single phase shifter 112, which may have varyingloss, controls the phase shift of the signals going to or coming fromthe antenna element 102 relative to the corresponding signals in theother RF front-ends 100.

The phase-invariant VGA 110 may be implemented as a single stage or may,alternatively, be implemented in multiple stages for improved gainrange, noise figure, and linearity, as shown below. Each of the RFfront-ends 100 has a similar structure, with settings for the VGA 110,the phase shifter 112, and the R/T switches 106 being determinedexternally as described below. In an alternative embodiment, there maybe a phase shifter 112 between the antenna 102 and R/T switch 106. In afurther embodiment, there may be a phase shifter 112 on each of thetransmit and receive paths.

Referring now to FIG. 2, a method for beam control in a phased-arraysystem is shown. Block 202 sets a phase at each RF front-end 100 usingthe respective phase shifter 112. The phase set by block 202 isdetermined by the desired antenna beam pattern and may be derived duringoperation or stored in, e.g., a lookup table. Block 204 sets a gain ateach RF front-end 100 using VGA 110 to compensate for gain at the phaseshifter 112 while block 206 further adjusts the gain to providetapering. If a change in tapering is needed at block 208, processingreturns to block 206 to adjust the gain, and if a change in beamdirection is needed in block 210, processing returns to block 202 to seta new phase. If no change is needed, transmission and reception canproceed as normal. It should be noted that the operation of switches maybe performed without triggering a change in beam pattern or tapering—thelinearity of RF propagation means that the beam pattern of the systemwill be the same regardless of whether the system is transmitting orreceiving.

Referring now to FIG. 12, three embodiments of a single-ended VGA 1200,1210, and 1220 are shown. Each embodiment includes a load 1202 (shown inthis example as an inductor to resonate with the capacitances of theinput transistor 1204 and any further stages). In each embodiment, thehigher the voltage applied to the input transistor 1204, the higher thegain of the respective amplifier. The input transistor is biased by a DCbias voltage V_(bias) 1205 and receives an input voltage V_(i). The biasvoltage controls the DC current flowing through transistors 304 and as aresult controls the gain of the single-ended VGA 1200, with a resistorhaving a value R_(e) that is selected to compensate for the phasebehavior of the transistor 1204. A second VGA 1210 is shown that has asimilar structure to the first VGA 1200 but with a variable resistor1216. The structure of this variable resistor 1216 will be described ingreater detail below. In the third embodiment 1220, a second transistor1228 is included with a respective DC biasing voltage V_(c). The secondtransistor 1228 improves the reverse isolation between input and outputnodes. Thus the introduction of a cascode does not interfere with thebenefits provided by a degeneration resistor.

Referring now to FIG. 13, a detailed diagram of the variable resistor1216 is shown. The variable resistor 1216 includes N branches, each ofwhich includes a respective resistor 1302 and a switch 1304 that is usedto activate its respective resistance. The variable resistor 1216therefore has a total effective resistance that is the combination ofeach of the activated resistances in parallel. This allows theresistance of the variable resistor 1216 to be tuned to provide aconstant phase response in a VGA.

Referring now to FIG. 3, a schematic of a single-stage, phase-invariantVGA 300 is shown. The VGA 300 is antisymmetric, taking a positive andnegative inputs, V_(i+) and V_(i−), and producing a positive andnegative output, V_(O+) and V_(O−). The gain control inputs 305 providea bias voltage to control respective transistors 304 that are, e.g.,bipolar junction transistors (BJTs) The higher the current through thecollector of the transistors 304, the higher the gain of the VGA 300.Each branch of the VGA 300 includes a variable resistor 306 thatcontrols the effect the VGA 300 has on the phase. It is thereforepossible to create a VGA 300 with a resistance value (R_(E)) of theresistor 306 that produces a stable phase shift across the range of theVGA's gain adjustment ability. The details of selecting R_(E) will beexplained in detail below. It should be understood that a cascodestructure may be used instead to achieve a higher gain and additionalisolation.

A supply voltage V_(DD) is provided through load inductors 302, whichare used to resonate the capacitance of the input transistors 304 andthe input capacitance of the next stage (if any). In general the loadcould be a resistor, an inductor in parallel with a capacitor, or acascaded device followed by one or more passive devices. The load of theamplifier 300 is designed to provide a predetermined gain and frequencyresponse. A tail inductor 308 connects the resistors 306 to ground. Inan alternative embodiment, this tail inductor 308 may be replaced by acontrollable current source. The tail inductor 308 forms ahigh-impedance to improve common-mode rejection. With the tail inductor308, the common gain is much lower than the differential-mode gain. If acurrent source is used instead of the tail inductor 308, the currentsource implements the high impedance at the common node and at the sametime provides further gain control. In this case, the DC voltage at thebase of the input transistors 304 would remain constant. In either case,the gain control mechanism is ultimately implemented through collectorcurrent of the input transistors.

Each of the above embodiments uses a resistance that is selected toprovide a relatively constant phase shift between the output and theinput of the VGA, across the different gain settings of the VGA. Theeffective transconductance of an amplifier in the single-sidedembodiments of FIG. 12, measured at the collector of transistor 1204 isgiven as:

$g_{m,{eff}} = \frac{g_{m,i}}{\left\{ {1 + {g_{m,i}R_{e}} + {{\left( {r_{b} + R_{e}} \right) \cdot j}\; {\omega \left( {C_{{be},{par}} + {\tau_{B}g_{m,i}}} \right)}}} \right\}}$

where g_(m,i) is the intrinsic device transconductance, R_(e) is theresistance of the degeneration resistor 1206/1216 external to thetransistor 1204, r_(b) is the base resistance of the transistor 1204, cois the frequency of operation, C_(be,par) is the g_(m,i) independentpart of the base-emitter capacitance, and τ_(B) is the base transit timeof the transistor 1204. When the value of g_(m,i) changes (e.g. byvarying the base to emitter voltage) then g_(m,eff) and the gain of theamplifier change as well, realizing the variable gain function of theamplifier. Normally, the phase of g_(m,eff) (and hence the phase of theVGA) will change with g_(m,i) as well which is undesirable in someapplications as explained above. In one embodiment, it can be shown fromthe equation above that if:

$R_{e} = \frac{\tau_{b}}{C_{{be},{par}}}$

then the phase of g_(m,eff) will not depend on g_(m,i), and hence thephase of the amplifier will remain relatively constant across gainsettings.

Referring now to FIG. 4, a method of designing a single-stage,phase-invariant VGA is shown. Block 402 lays out the general circuit,including the transistors 304. Block 403 obtains the BJT's intrinsictransconductance, resistance and capacitance values from simulation, andblock 404 then determines the transistor base transit time. Based onthese quantities, block 406 determines a resistor degeneration valueR_(E), where R_(E) is equal to the ratio of the transit time and theg_(m)-independent base to emitter capacitance—notably, parasiticsbetween, e.g., metal contacts and other incidental components do notplay a significant role. Block 408 then designs the single-stage,phase-invariant VGA using the determined resistance value RE. Block 410then verifies the phase invariance by, e.g., simulating the completecircuit and varying the gain to determine the degree to which the phasevaries.

Referring now to FIG. 5, a more detailed embodiment of the single-stage,phase-invariant VGA 300 is shown. Instead of the variable resistors 306,an actively controlled resistor network 500 is shown. The resistornetwork 500 provides a tunable effective resistance, with a differentresistance between the emitters of the switches 504 and 506 depending onwhether the switches 504 and 506 are open or closed. The effectiveresistance degeneration values result in different slopes of phaseversus gain. The values of resistors 502, 506, and 510 are selected tocontrol that slope, between positive slope, no slope, negative slope,all-positive but varying in degree, all-negative but varying in degree,or constant slope. This provides for many different phase dependenceconfigurations and can provide correction for process variations.

Referring now to FIG. 6, a general diagram of a two-stage,phase-invariant amplifier 600 is shown. The two-stage amplifier 600includes a first VGA stage 602 and a second VGA stage 604. One of thetwo stages is designed independently of phase considerations, while thesecond is designed to compensate for phase dependencies in the firststage—the latter is referred to herein as the “phase-varying” or“phase-compensating” stage and has a phase response that is controlledto be the opposite of that in the independent stage. In one embodiment,the first stage 602 is designed independently of phase considerationsand the second stage 604 is designed to compensate for the phasedependencies of the first stage 602. In a second embodiment, the secondstage 604 is designed independently of phase considerations and thefirst stage 602 is designed to compensate for the phase dependencies ofthe second stage 604. The two-stage amplifier 600 provides more degreesof freedom and a larger gain range than the single-stage amplifier 300while maintaining phase invariance.

Regardless of which stage is selected as the phase-varying stage, thestructure of FIGS. 3 and 5 may be used, with a value of R_(E) beingselected to produce a phase dependence in the phase-compensating stagethat is the opposite of that present in the independent stage. In onespecific embodiment, where the first stage 602 is designed independentof phase considerations, the second stage 602 has the structuredescribed in FIGS. 3 and 5 with a value of R_(E) that provides aninverse phase dependence as compared to the first stage 602.

Referring now to FIG. 7, graphs showing the gain and phase relationshipsof the two stages are shown. A first graph shows gain on its verticalaxis and a control signal on its horizontal axis, indicating the gainbehavior of the VGAs 602 and 604. A first signal 702 represents the gainof the first stage 602 and a second signal 704 that represents the gainof the second stage 604, with a third signal 706 showing the gain of thetwo stages together.

In the second graph, the phase relationship of the two VGAs 602 and 604is shown, with the vertical axis showing the phase of each stage and thehorizontal axis shows the same control signal as in the first graph. Afirst signal 708 represents the phase dependence of the first stage 602,while a second signal 710 represents the phase dependence of the secondstage 604. The sum of the two signals is shown as 712 and shows a flatresponse to the control signal, such that the effect of the two stagesin combination is phase-invariant.

Referring now to FIG. 8, a method of designing a two-stage,phase-invariant VGA 600 is shown. Block 802 designs one stage that isindependent of phase dependency considerations. This stage may be eitherthe first stage 602 or the second stage 604 and should be designed tohave a low noise figure. Block 804 simulates the phase dependence of theindependent stage on gain control to determine its behavior. Block 806then lays out the circuit for the phase compensating stage (which is theother of the first stage 602 and the second stage 604). Block 808obtains the transistor's intrinsic transconductance, resistance andcapacitance values from simulation of the phase compensating stage andblock 810 then determines the transistor base transit time. Based onthese quantities and the phase dependence of the independent stage,block 812 determines a resistor value R_(E) where the phase dependenceof the phase compensating stage cancels the phase dependence of theindependent stage. Block 814 then designs the phase-compensatingamplifier stage with the determined resistance value R_(E). Block 816verifies the phase invariance of the two-stage VGA 600 by, e.g.,simulating both stages and varying the gain to determine the degree towhich the output phase varies.

Referring now to FIG. 9, an alternative embodiment is shown of adifferential VGA 900 that provides ±90 degrees of phase shift at aconstant amplitude. This embodiment includes varactors 902 which, astheir capacitance varies, changes the phase output with respect to theinput from, e.g., +90 to −90 degrees. While the gain would normallychange during such phase control, the variable resistors 306 of thepresent embodiments are designed to compensate for the gain variationwithout affecting the selected phase, producing a gain-invariant phaseshifter. The variable resistors 306 may be designed according to theresistor network 500 or any other appropriate circuit. Thus the VGA 900provides both phase control and gain control. In one embodiment, the VGA900 may be controlled using autonomic feedback, where the power outputof the VGA 900 is measured and used to control the input voltage attransistors 304 to maintain a constant desired gain.

Referring now to FIG. 10, an alternative embodiment is shown thatprovides a gain-invariant 360° phase shifter 1000. The phase shifter1000 includes two pairs of cascode transistors 1002 between thevaractors 902 and the input transistors 304 of the 180-degree phaseshifting VGA 900. The transistors 1002 exploit the differential natureof the VGA 1000 to invert the phase change by choosing whether V_(b1) orV_(b0) is high or low. Only one of the inputs V_(b0) and V_(b1) isactive at one time, with the other being pulled to ground.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

It is to be understood that the present invention will be described interms of a given illustrative architecture having a wafer; however,other architectures, structures, substrate materials and processfeatures and steps may be varied within the scope of the presentinvention.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

A design for an integrated circuit chip may be created in a graphicalcomputer programming language, and stored in a computer storage medium(such as a disk, tape, physical hard drive, or virtual hard drive suchas in a storage access network). If the designer does not fabricatechips or the photolithographic masks used to fabricate chips, thedesigner may transmit the resulting design by physical means (e.g., byproviding a copy of the storage medium storing the design) orelectronically (e.g., through the Internet) to such entities, directlyor indirectly. The stored design is then converted into the appropriateformat (e.g., GDSII) for the fabrication of photolithographic masks,which typically include multiple copies of the chip design in questionthat are to be formed on a wafer. The photolithographic masks areutilized to define areas of the wafer (and/or the layers thereon) to beetched or otherwise processed.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Referring now to FIG. 11, a system 1100 for controlling the phased-arrayfront-ends 100 is shown. The system 1100 includes a hardware processor1102 and memory 1104. The system 1100 further includes one or morefunctional modules. In one embodiment, the modules may be implemented assoftware that is stored in memory 1104 and executed by hardwareprocessor 1102. In an alternative embodiment, the modules may beexecuted as one or more discrete hardware components, for example in theform of application specific integrated chips or field programmable gatearrays.

A phase control module 1106 controls the phase shifters 112 inaccordance with a desired beam pattern. A gain control module controlsthe phase-invariant VGAs 110 to provide trimming. As described above inFIG. 2, the phase and gain may be adjusted as needed, but the iterativephase/gain refinement that is present in conventional systems is notperformed in the present embodiments. Instead, because the VGAs 110 havea phase shift insensitive to gain, the phase and gain may be setindependently of one another. An R/T switch control issues commands tothe R/T switches 106 during operation to switch between transmit andreceive modes.

Referring now to FIG. 14, a system for designing a phase-invariant VGAis shown. The system 1400 includes a hardware processor 1402 and memory1404. The system 1400 further includes one or more functional modules.In one embodiment, the modules may be implemented as software that isstored in memory 1404 and executed by hardware processor 1402. In analternative embodiment, the modules may be executed as one or morediscrete hardware components, for example in the form of applicationspecific integrated chips or field programmable gate arrays.

A circuit layout module 1406 provides a circuit layout for a one-stageor two-stage VGA. A simulation module 1408 simulates the VGA, which fora single-stage embodiment includes simulating properties of the inputtransistor(s). For a two-stage embodiment, simulation further includessimulating the dependence of the phase of one stage on the gain of thatstage. A resistance module 1410 calculates a suitable value for R_(E),either for the single-stage VGA or for the phase-compensating stage of atwo-stage VGA. The circuit layout module then employs the determinedR_(E) value to complete the VGA design.

Having described preferred embodiments of dynamic phased array taperingwithout phase recalibration (which are intended to be illustrative andnot limiting), it is noted that modifications and variations can be madeby persons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

1. A variable gain amplifier, comprising: a first amplifying transistor configured to receive a first input signal and to provide a first amplified output signal based on the first input signal; and a phase compensating resistor connected to the first amplifying transistor and having a resistance calibrated as: $R_{e} = \frac{\tau_{b}}{C_{{be},{par}}}$ where τ_(b) is the base transit time of the first amplifying transistor and C_(be,par) is the gain-independent part of the base-emitter capacitance of the first amplifying transistor.
 2. The variable gain amplifier of claim 1, wherein the phase compensating resistor comprises a variable resistor network connected between the first amplifying transistor and ground.
 3. The variable gain amplifier of claim 2, wherein the variable resistor network comprises a plurality of parallel branches, each comprising a respective resistance and a switch configured to activate the respective branch, wherein a total resistance of the variable resistor network is a parallel combination of resistances of resistors in activated branches.
 4. The variable gain amplifier of claim 1, further comprising a second cascode transistor, disposed between the first amplifying transistor and a biasing voltage, that is configured to improve reverse isolation between an input signal and the output signal.
 5. The variable gain amplifier of claim 4, wherein the phase compensating resistor comprises a variable resistor network connected between emitter terminal of the first amplifying transistor and ground.
 6. The variable gain amplifier of claim 1, further comprising a second amplifying transistor configured to receive a second input signal and to provide a second amplified output signal based on the second input signal, wherein the phase compensating resistor is further connected to the second amplifying transistor.
 7. The variable gain amplifier of claim 6, wherein a polarity of the first input is opposite to a polarity of the second input and wherein a polarity of the first output is opposite to a polarity of the second output.
 8. The variable gain amplifier of claim 6, wherein the phase compensating resistor comprises a variable resistor network connected between emitter terminals of the respective amplifying transistors and ground.
 9. The variable gain amplifier of claim 1, wherein the phase compensating resistor has a resistance that compensates for a phase dependence of the first amplifying transistor, such that an output phase of the amplified output signal is dependent only on the phase of the input signal and is independent of an amplification of the first amplifying transistor.
 10. A variable gain amplifier, comprising: a first amplifier configured to receive a first input signal and to provide a first amplified output signal based on the first input signal; a second amplifier configured to receive a second input signal and to provide a second amplified output signal based on the second input signal; and a phase compensating resistor connected to the first amplifier and to the second amplifier and having a resistance that compensates for a phase dependence of the first amplifier, such that an output phase of the amplified output signal is dependent only on the phase of the input signal and is independent of an amplification of the first amplifier.
 11. The variable gain amplifier of claim 10, wherein the phase compensating resistor has a resistance calibrated as: $R_{e} = \frac{\tau_{b}}{C_{{be},{par}}}$ where τ_(b) is the base transit time of the first amplifying transistor and C_(be,par) is the gain-independent part of the base-emitter capacitance of the first amplifying transistor.
 12. A method of constructing a variable gain amplifier, comprising: designing out a circuit for a first variable gain amplifier that comprises: a first amplifying transistor configured to receive a first input signal and to provide a first amplified output signal based on the first input signal; and a phase compensating resistor connected to the first amplifying transistor and having a resistance that compensates for a phase dependence of the first amplifying transistor, such that an output phase of the amplified output signal is dependent only on a phase of the input signal and is independent of an amplification of the first amplifying transistor; determining parameters of the first amplifying transistor; determining a resistor degeneration value based on the parameters of the first amplifying transistor as: $R_{e} = \frac{\tau_{b}}{C_{{be},{par}}}$ where τ_(b) is the base transit time of the first amplifying transistor and C_(be,par) is the gain-independent part of the base-emitter capacitance of the first amplifying transistor; and constructing the first variable gain amplifier with the phase compensating resistor having a resistance equal to the resistor degeneration value.
 13. The method of claim 12, wherein determining parameters of the transistor comprises simulating the transistor to determine transconductance, resistance, and capacitance values. 